Inclusion of unique four-clawed crown-like nitrate–water cluster [(NO3)6(H2O)6]6− anions into the inter-spaces of a 3D H–bonded cationic net formed by a cationic calix[4]arene

Abstract

Reaction of 5,11,17,23-tetramino-25,26,27,28-tetrahydroxy-calix[4]arene (1) with MeI and NaOAc·3H2O in DMF produced a tetracationic calix[4]arene [H4L]I4 (2) {H4L = [5,11,17,23-tetrakis(trimethylammonium)-25,26,27,28-tetrahydroxycalix[4]arene]} in 90% yield. Anion exchange of 2 with [Ag(MeCN)4](PF6) in MeCN afforded [H4L](PF6)4 (3). Treatment of 3 with Na2CO3 or NaNO3 in MeCN afforded two mono-deprotonated complexes [H3L](PF6)3·MeCN (4·MeCN) and [(H3L)2{(NO3)6(H2O)6}]·4MeCN (5·4MeCN). Compounds 4·MeCN and 5·4MeCN have been characterized by elemental analysis, IR spectra, 1H NMR, and single-crystal X-ray crystallography. 4·MeCN contains a 3D cationic H–bonded [H3L]n3n+ net in which PF6− anions are embedded into its 1D channels. 5·4MeCN consists of another 3D cationic H–bonded [H3L]n3n+ net in which the unique four-clawed crown-like nitrate–water cluster [(NO3)6(H2O)6]6− anions are included into the inter-spaces between the layers of [H3L]3+ trications. The formation of this nitrate–water cluster anion may demonstrate interesting information about the hydration of nitrate in water-related systems.